title: Selective genomic targeting by FRA-2/FOSL2 transcription factor: regulation of the Rgs4 gene is mediated by a variant activator protein 1 (AP-1) promoter sequence/CREB-binding protein (CBP) mechanism.
abstract: FRA-2/FOSL2 is a basic region-leucine zipper motif transcription factor that is widely expressed in mammalian tissues. The functional repertoire of this factor is unclear, partly due to a lack of knowledge of genomic sequences that are targeted. Here, we identified novel, functional FRA-2 targets across the genome through expression profile analysis in a knockdown transgenic rat. In this model, a nocturnal rhythm of pineal gland FRA-2 is suppressed by a genetically encoded, dominant negative mutant protein. Bioinformatic analysis of validated sets of FRA-2-regulated and -nonregulated genes revealed that the FRA-2 regulon is limited by genomic target selection rules that, in general, transcend core cis-sequence identity. However, one variant AP-1-related (AP-1R) sequence was common to a subset of regulated genes. The functional activity and protein binding partners of a candidate AP-1R sequence were determined for a novel FRA-2-repressed gene, Rgs4. FRA-2 protein preferentially associated with a proximal Rgs4 AP-1R sequence as demonstrated by ex vivo ChIP and in vitro EMSA analysis; moreover, transcriptional repression was blocked by mutation of the AP-1R sequence, whereas mutation of an upstream consensus AP-1 family sequence did not affect Rgs4 expression. Nocturnal changes in protein complexes at the Rgs4 AP-1R sequence are associated with FRA-2-dependent dismissal of the co-activator, CBP; this provides a mechanistic basis for Rgs4 gene repression. These studies have also provided functional insight into selective genomic targeting by FRA-2, highlighting discordance between predicted and actual targets. Future studies should address FRA-2-Rgs4 interactions in other systems, including the brain, where FRA-2 function is poorly understood.
authors.affiliation: School of Biosciences, Cardiff University, Cardiff CF10 3AX, Wales, United Kingdom.
authors.forename: Jeff S
authors.initials: JS
authors.lastname: Davies
authors.forename: David C
authors.initials: DC
authors.lastname: Klein
authors.forename: David A
authors.initials: DA
authors.lastname: Carter
mesh_terms: D000818:Animals; D050882:CREB-Binding Protein / Q000378:metabolism*; D002940:Circadian Rhythm / Q000235:genetics; D051921:Fos-Related Antigen-2 / Q000235:genetics*; D005786:Gene Expression Regulation / Q000502:physiology*; D014644:Genetic Variation; D016678:Genome; D011401:Promoter Regions, Genetic; D020710:RGS Proteins / Q000235:genetics*; D051381:Rats; D055647:Rats, Transgenic; D018808:Transcription Factor AP-1 / Q000235:genetics*
chemical_list: D051921:Fos-Related Antigen-2; C497874:Fosl2 protein, rat; D020710:RGS Proteins; D018808:Transcription Factor AP-1; C098799:RGS4 protein; D050882:CREB-Binding Protein; C494365:Crebbp protein, rat